1. Field of the Invention
The present specification relates generally to a low voltage differential signal (“LVDS”) transmitting circuit and an optical disc recording apparatus employing the LVDS transmitting circuit, and particularly to an LVDS transmitting circuit and optical disc recording apparatus capable of suppressing unevenness of an output voltage.
2. Discussion of the Background Art
In accordance with the recent downsizing and speeding up of an integrated circuit, LVDS circuits are becoming more widely used as a signal transmission device. In order to handle a differential signal of small amplitude, it is generally desirable for a low voltage differential signal transmitting circuit (“LVDS circuit”) to have a prescribed precision so as to transmit precisely such a small differential signal between a driver circuit and a receiver circuit.
In a semiconductor integrated circuit, performance generally varies in accordance with unevenness of a process and changes in temperature and power supply voltage or the like. As a result, precision is difficult to obtain in transmitting a small signal and is often a problem. In order to resolve such a problem, Japanese Patent Application Laid Open No. 2000-134082 proposes a technology in which a MOSFET is employed in each of a plurality of output circuits, each handling an LVDS so as to adjust a current that drives a driver. Further, one of the plurality of output circuits is utilized as a dummy in which a terminal resistor is connected to output terminals thereof so as to form High and Low level signals. A prescribed control signal capable of controlling the MOSFET to generate and output the High and Low level signals of the prescribed levels is generated. The control signal is then supplied to the MOSFETs included in the remaining output circuits in order to automatically adjust respective currents.
By enabling adjustment of a current value in such a way at a signal transmission site, amplitude of a differential voltage output from a driver circuit can conventionally be controlled to be constant. However, a particular circuit is necessitated for adjusting a current, and as a result a number of elements increases in the circuit.